The present invention relates to an insulating plate of a nonaqueous electrolyte secondary cell, a nonaqueous electrolyte secondary cell, and a method for producing an insulating plate of a nonaqueous electrolyte secondary cell.
As shown in FIG. 16, a rolled nonaqueous electrolyte secondary cell (lithium ion cell) 100 includes a cell element 101 serving as a power generation element and a nonaqueous electrolyte solution 102 serving as a medium for moving ions between a cathode and an anode, the cell element 101 and the nonaqueous electrolyte solution 102 being housed in a cylindrical can body 103 with a bottom made of a conductive metal or the like. An opening of the can body 103 is sealed with a cover member 104 so that the inside is sealed in an airtight state.
The cell element 101 includes strip-shaped cathodes 105 formed by applying a cathode mixture coating solution, which is prepared by uniformly dispersing a cathode active material, a conductor, and a binder, to a cathode current collector and strip-shaped anodes 106 formed by applying an anode mixture coating solution, which is prepared by uniformly dispersing an anode active material, a conductor, and a binder, to an anode current collector. The strip-shaped cathodes 105 and the strip-shaped anodes 106 are stacked with separators 107 between the adjacent strip-shaped cathodes and anodes 105 and 106, and the stack is rolled in the longitudinal direction of the cell. In addition, an insulator 108 serving as an insulation member is disposed at the opening-side roll end. The cell element 101 is housed in the can body 103 together with the insulator 108.
The can body 103 is formed in a cylindrical shape with a bottom using, for example, iron, nickel, stainless steel, or the like. The opening of the can body 103 is sealed with the cover member 104 to form a cell can 109. Further, a bead portion 110 is provided as a constriction along the inner periphery near the opening of the can body 103 so as to be used for positioning when the cover member 104 is disposed. Therefore, the cover member 104 positioned on the bead portion 110 is attached to the can body 103 by bending inwardly the edge of the can body 103, which is positioned above the cover member 104, i.e., caulking.
The nonaqueous electrolyte secondary cell 100 is formed through the assembly step of housing the cell element 101 in the can body 103 of the cell can 109, and thus a space is provided between the cell element 101 ad the cell can 103.
For example, when the nonaqueous electrolyte secondary cell 100 is used for an electric tool, the cell element 101 three-dimensionally reciprocates in the cell can 103 due to vibration of the electric tool, thereby causing fracture, breakage, bending, or the like. As a result, the nonaqueous electrolyte secondary cell 100 may become unusable.
In order to resolve such a problem, therefore, there have been proposed a method of fixing the cell element 101 by caulking the can body 103 of the cell can 109 from the outside (for example, Japanese Unexamined Patent Application Publication No. 2003-297301), a method of fixing the cell element 101 by housing the cell element 101 in the can body 103 of the cell can 109 and then expanding the diameter of the cell element 101 from the inside to press the cell element 101 into contact with the inner surface of the can body 103 (for example, Japanese Unexamined Patent Application Publication No. 11-97301), etc.